To possibly improve protein balance, we studied the effects of growth hormone (GH) on whole body protein metabolism and on synthesis of hepatic export proteins albumin and VLDL apolipoprotein B in 10 patients after liver transplantation. Five patients received only standard postoperative treatment (controls), 5 patients were given additionally GH (2x8 I.U. per day for 14 days). Calorimetry and 4h-tracer leucine infusions were performed 5 days after surgery. Tracer incorporation was measured for albumin by IRMS (N=6), for apoB by GCMS (N=10). The clinical course was similar for both groups. Cumulative urea nitrogen excretion (days 1-4, X D(SD) tended to be lower after GH: CO 60. Differences in leucine oxidation , protein breakdown 145 and non-oxidative leucine disposal were not statistically significant. Plasma albumin levels , fractional synthetic rates (0.22(0.13 vs 0.15(0.07 pools/day) and albumin production were similar. In conclusion, after major surgery, GH tends to lower nitrogen excretion and increase total body protein turnover without affecting hepatic export protein synthesis.